So my '74 /6 conversion with the DWD sump tank is slowly leaking down into the engine sump. I have a leaking #6 rocker shaft that I'll have to R&R so I know my engine is full to at least to the exhaust rockers. I know it doesn't drain enough to do this if I drive at least weekly. I have a buddy who's well worn engine has hydrolocked a few times due to this.
I had to start and move the car, quite the smoke show.

Only automatic cure I've seen so far is a $300 valve from Rothsport. Or I could just install a ball valve and red tag my dash for just over $20.

I know it's a common 911 issue, do you other /6 owners have this issue and what do you do about it?

I just drain the oil each time I move the car from the trailer to the garage.... never leaks that way

Only logical solution is to drive it daily. But being in Ontario, you have the same problem as me . . . Winter.

Worn(ish) oil pump gears won't help but honestly even perfectly new gears will still bypass oil over time.

A long time ago I worked on suspension project that used hydraulics to control vehicle ride height. The project was eventually cancelled because over time, hydraulic fluid would eventually leak past the closed orifice valves and the vehicle would go unlevel. Imagine coming home from a 3 week vacation and finding your vehicle at the airport listing to one side like a sinking ship. Of course it would level out upon start up but it sure looked stupid! Even super precision control valves (i.e. high $$) still leaked, they only slowed the rate of leakage. The project was doomed financially due to the cost of the control valves and the inability to find an economical valve that wouldn't leak over extended periods of time.

I don't think there is a total solution. I would expect the anti-drainback valve to leak down over time too. It would just be a whole lot longer periof of time.

This is the crux of a dry sump, especially one with the tank above the engine.

I'll be watching this one.

your pretty handy , the Porsche part is $125, needs some creativity = time=$$

https://www.911partsdirect.com/shop/996-99-...-metzger-motor/


Im going to use a in hand manual ball valve..my Tank is even higher in the rear trunk...maybe this 12 volt.. Everyday driver for yrs no problem, Instaled in another 14 sits alot,,and its an experience to start... although it doesnt smoke much .

https://www.amazon.com/Motorized-Stainless-...rial&sr=1-2

You mean people didn't like the Citroen DS look? I have a coworker who drives a DS21 almost daily in the winter ( I know-his summer car is a Saab 96 with something like 750k on it) and always loved watching it pump back up from "low position."


I'm not a huge fan of adding the check valve in the top link. You're adding an "undetectable" failure point, especially in terms of partial open failures.

Strong opinion to follow but...absolutely do not use a motorized ball valve. I have not found a motorized ball valves under ~$1500 that doesn't suck (after over a decade of dealing this these kind of components). Eventually they all fail and to be safe you have to watch them-at that point you might as well have a manual ball valve and lock-out tag-out like your original idea. I would never buy one without position feedback that would prevent the car from starting on event of a non-open. Not worth it.

My dad's 911 sits a lot too. We've resigned to letting it smoke on startup and kinda cough to life.

@JD74914

It was the early 2000's and as young engineers we thought we certainly could solve the Citroen DS problem with "modern" valves and a less complex hydraulic system.

Agree completely to not use motorized valve without position feedback. They all fail eventually in whatever position you don't want.

I haven't had this issue but mine is a baby "six",the larger motors have more oil for what is most likely not a much larger crankcase than mine...maybe that's the reason,I run 9 litres and have found that is ok with a stock oil tank but no front cooler.
In my case the oil pressure comes up very quickly on cranking so can only presume the excess (drain back) of oil is being returned to the tank as quickly.
Perhaps a ignition remote shutoff would help so you crank for a while extra and the pump scavenge clears the sump oil before the engine starts if the car has been sitting for a while.

https://www.amazon.com/Everflow-Supplies-21...C202&sr=8-5

Horizontal installation only. Approved for water, oil and gas to 150psi.

Not really so good when you add acceleration (either lateral or longitudinal depending on what direction you orient it). That’s why it says horizontal installations only because it can’t handle gravity. Swing checks are never really a tight shutoff either.

Almost Every war bird in thd chino planes of fame
Have drip pans for their hydraulics
From a p47

To f18 /f14

But not the stearmans ... No hydraulics except maybe the prop

Is yours leaking by through the pressure or scavenge side?

If scavenge, how about something like this?:

http://www.improvedracing.com/oil-accumula...alve-p-555.html

Flapper valve.

Those rockers are a pain... just finished mine last night. Am trying those RSR seals this time.

Just a thought , what about a electric pump just to scavenge oil out of sump
and pump back to tank ?

https://tiltonracing.com/product/cooler-pumps/

https://www.rbracing-rsr.com/oilsystems.htm

what about adding a manual shut off valve to the oil feed line, use it only for prior to long term parking. that should stop oil sipping back into the sump. downside is it needs to be open prior to starting engine.

just a thought

had this problem on my nortons and indian. they sit, oil runs into the crankcase. I have seen bsa owners put in valve or ball checks, I have also seen what happens when you forget to turn the valve on or the check ball fails. I am good with drip pans and emptying the crank case upon start up. if it sat long enough for oil to drain into case, it will probably need other fettling as well.

Feed side, the pump I blueprinted and DFL coated the inner housings, but it's just a pump, nothing the way of a check valve.

The rockers I have RSR seals and they still leaked and came loose. Last year I had this issue with #1 and 2 rockers, a buddy sent me an article by CE where they said to install the shafts 100% dry and clean. So far the 1/2 rockers are dry, so a PITA job before next season is to R&R the rest of the rockers.
I think I'll add a ball valve for storage when I tackle the rockers.

Would That improved racing check valve be a good alternative to the 3x more expensive Rothsport valve (available for slightly less from Wilhoit)?

Can’t quite get my head around what you would need to fit it into a 6 oil feed line - a female fitting that fits the line and then an AN to metric adapter at the other end. By the time you do that you are almost at the price of the Rothsport valve.

Anyone have any further experience with that?

that check valve has a 1lb opening rate the facory/rothsport is 3lbs,,,and since its a check flapper , you would actually have to install it backwards..... Its the continual flow from the tank is what is trying to be lightly blocked when not running.. ie keeps the oil in the tank..at rest...little to no restriction while running....

Im gonna use the manual ball valve also..mine will be right below trunk floor ,,so the handle can be inside the rear trunk... My setup is kinda odd, But I have a huge front trunk...

Yea after thinking about it more, the improved racing valve is a back flow preventer while the Rothsport valve prevents forward flow at low pressure buts allows full flow with pressure.

Yea after thinking about it more, the improved racing valve is a back flow preventer while the Rothsport valve prevents forward flow at low pressure buts allows full flow with pressure.

Or maybe better described as a check valve with very low opening pressure.

I did the valve, but I got it from Engine Builders Supply. They’re local to me. It was less than $300 though.

This whole thing scares me.. Wow can you imagine if any of these devices failed.. Over all the years of owning 911 flat sox engine only saw 1 hydro lock and that was after 2 years sitting.. We rotated the engine backwards and all was good.

Just a thought. During the off season. why don't you pull the plugs and crank the motor for a minute? It would squirt out any oil in the cylinders and pump some oil to the tank. Take a before and after measurement of oil in the tank. Repeat? Maybe if you did this frequent enough you could get away with just disabling the ignition and cranking the engine. Or leaving the plugs loose for the season and doing this every few weeks? Idk the pumping rate of the oil pump at start up. Well hell, maybe you could just start it up every few weeks and put a fan on...

Wilhoit says that the flapper is held closed by a very light spring and will open if the spring breaks. They emphasize that valve failure cannot cause oil starvation.

I’m tired of the smoky start up and associated ills. Installing mine sooner than later.

Interesting but I have to ask; wouldn't the flow of oil keep the gate open no matter the imposed G forces? And wouldn't a good American made check valve, not a cheap import, with an ASME WOG rating seal well? Not testing you. I realize you're an engineer and I but a plumber.

I’m always hesitant to place anything in the oil feed line as it’s function of providing a good oil supply to the pump is critical. But I have had the car look like I’m fogging the neighborhood for mosquitos after sitting for an extended time.